Among the most popular attractions of this year’s CAFECONF Linux conference down in Argentina, the “Buenos Aires Libre” group, is promoting its hobbyist, city-wide “community network”. While other groups here were handing out leaflets or showing software on a PC screen – or in the case of La Intella, a dual-core notebook – the folks from Buenos Aires Libre caught everyone’s attention because they had hacked open hardware on display, including open boxes, cables, and a Linksys WRT54G housed in a waterproof case with a large omni antenna. I used the opportunity to have a chat with Martin Seeber who was there promoting the effort and who runs one of the main nodes. I also had a little chat with some of his peers and needless to say I learned a lot.

Unlike other Wi-Fi “projects” and “communities” like the (in)famous FON which mixes business objectives with grassroots participation, this one isn’t about providing hotspots for public internet use, and it isn’t commercial at all. B.A. Libre – BAL hereinafter – aims to run a network with its own backbone, capable of routing traffic between nodes even if the Internet goes down, it doesn’t rely on the public internet for transportation. The project was kick-started by a handful users a long six years ago and after several iterations and change of structure and leadership, now seems to show steady progress.

The BAL network spine uses point-to-point links and directional antennas along with inexpensive consumer Wi-Fi APs or in some instances full PCs in waterproof enclosures- loaded with their own customized Linux software, dubbed Obelisco – Spanish for ‘obelisk’ the city’s landmark.

Three years ago, at the time the local local loop monopoly covering the northern half of this country decided to charge for DSL traffic above a certain quota – a decision it later dropped – the company suddenly found itself uncomfortably in the public spotlight, and facing the heat of the angry users and ISPs who demanded local loop unbundling. One exec at the behemoth telco lost his composure and reportedly exclaimed at a congress hearing on the subject: “If you want traffic to be free on the network, then build your own”. Well, ironically, that’s precisely what these folks have been doing: building their own backbone.

Interesting facts
For their backbone, they choose to use an “extended star” or tree topology, avoiding the use of Mesh technology because of performance problems, as the number of hops increases. This BAL network backbone currently uses 802.11b/g equipment on the 2.4GHz band. It also doesn’t use WEP, WPA, or any other encryption, just MAC address filtering, so if you want to connect to a given node you must first register on the BAL system as a project member, and then ask the target node for permission so he can add your equipments’ MAC address to the nodes’ white list. Users concerned about the safety of their data are encouraged to run OpenVPN to create tunnels in such instance. Some nodes, not all, also sport an omni-directional secondary antenna so that nearby clients all around can connect as well.

I asked them if they had any run-ins with the airwaves watchdog and their response was an emphatic no. There’s a regulation making selling VOIP or telephony services using Wi-Fi equipment strictly and specifically forbidden by the airwaves watchdog, but it’s aimed at ISPs. First BAL is a non-profit endeavour, a community network, and it doesn’t aim to provide any specific services, just inter-connect computers. Thus the local regulating authority gives them no hassle at all because such non-profit usage falls within the ‘private use’ considerations of the local regulations.

On the software/organisation aspect, they have done a quite impressive job. The Wiki shows a lot of work, and there’s even an on-line map built using Google Maps satellite images and showcasing all nodes and clients, and which are currently active. The registration/membership system is also well done. Dubbed the “BA Libre Location System” or BALLS for short, the project’s web map lists 259 “points of interest”, that is, either nodes or users who have decided to take part in this project in the whole capital city and its metro area of influence, with 13 on-line nodes and APs in BA city at the time of this writing. There is also a Wiki, an IRC channel and mailing lists.

Annoying landlord? Hack a satellite dish!
When I saw the pictures and the kind of relatively huge equipment some had installed – think a mid tower to mini-tower waterproof metal box hooked to a building’s TV antenna tower- or huge directional parabolic grid antennas, one question kept circling my mind: “What if the landlord of building’s superintendent doesn’t allow me to install such a large antenna?”. I asked the guy next to me in the BAL booth. He thought for a second and replied with a smile: “Well, as far as testing goes… you can always mod a satellite dish, and replace the LNB with a biquad. very few people, if any, will notice”.

He told me one of the nodes even installed one. And yes indeed, there’s even a picture of such a mod on their Wiki, and although I wouldn’t call it unnoticeable, it proves that nothing can stop this pack of motivated geeks from reaching their common goal.

The best way to understand slow scan TV is to imagine it as colour fax pictures but sent over the radio rather than the phone. The pictures are transmitted via tones (1200-2300 HRZ) over the air. There are several simple ways to get setup for slow scan TV, the simplest of which use your computer and software with a hardware interface. There are interface circuits which work excellent and cost less than $20 to build or nil if from your junk box.

My experience with slow scan has been great fun. I’ve exchanged picture QSLs with different people in many different countries throughout the world. The quality of the pictures is somewhat dependent upon the computer, (monitor & graphics card), and somewhat on the software, hardware. The better systems support Hicolour which gives typical picture resolutions of 320 x 240 in 32 thousand colours. These pictures are almost photographic quality and are very impressive to say the least. Once you’ve tried it your hooked. Imagine being able to swap mug shots with other Amateurs. See who you’re talking to. Send diagrams and schematics over the air. It’s great. Listen to HF on 14.230 and 14.233 almost anytime to hear the action.

HANDBOOKhttp://web.archive.org/web/20030207194354/users.rcn.com/sstv/handbook.htmlftp://ftp.amsat.org/amsat/software/PC/fax-sstv/jvfax70.ziphttp://www.kent.net/ve3rdn/overview.html
“If your interested at all, take the time to build up the simply 741 op-amp circuit described in the JVFAX info and run the JVFAX70 software available right here (above, 736K). This system works great and is simple to setup and use. The interface circuit is made up of only a 741 op-amp, couple caps, and a couple resistors. The interface circuit plugs into a serial port (com port) of any IBM compatible type computer, 386 or up recommended. One connection from the interface to the speaker output and your copying pictures. See articles for details on connections for transmit and more info on the different systems being used. There’s even software available to copy and send SSTV using your sound card.”

GUERRILLA TELEVISIONhttp://wiki.stealthiswiki.org/wiki/Guerrilla_Television
Experience Behind the Iron Curtan
“Before the downfall of the Soviet Union, there were a number of pirate TV operations scattered around Eastern Europe. Many were guerrilla style hit-and-run operations that would rig up a low-tech transmitter with a junked VCR, set to go on the air during the official government newscast, overriding the signal for several blocks. When the authorities found the transmitter, often on the roof of an apartment house or in an vacant building, they would find home-built equipment that had been abandoned, rigged to a timer switch. Much of the programming was very short (since the authorities would be searching for the source within minutes) and usually consisted of recordings from foreign broadcasters like Voice of America and Radio Free Europe, with still photos for visuals. One brave pirate in Moscow would show a tape of the official government news broadcast, with someone else’s voice dubbed onto the soundtrack, reading uncensored news peppered with dirty jokes.

In 1985, some very brave astronomers from Poland’s University of Torun used home-made equipment to superimpose pro-Solidarity slogans over the images of the state-run TV network. [1] You can imagine how the viewing public (as well as the authorities) must have felt when, during the official government news broadcast, the words “SOLIDARITY TORUN: ENOUGH OF PRICE HIKES, LIES AND REPRESSION” flashed on the screen.

In 1977, back when the UK used analogue television, someone identified as “Vrillion” of the “Ashtar Galactic Command” over-rode the audio channel of England’s Southern Television for 6 minutes.”

Free-To-Air Satellite TV
In many rural parts of the USA, a big thing is “Free-To-Air” (FTA) TV dishes. These are common in the UK and parts of Europe, but are only starting to pick up in the USA. You’ll need an unobstructed view of the Southern sky, room for a dish (with a directional motor so you can watch more than one satellite) and a receiver box. A decent set-up will set you back about $200-300 plus installation, but there’s no monthly fees. You won’t get Dish Network or DishTV (and if you do without subscribing, they’ll sue you for Theft of Services), but there’s lots of TV and radio channels to be had, as well as network TV station feeds. Depending on where you are, you can also watch foreign broadcasts. The forum at DSSRookie is a good place to start, as well as the FTA forum at SatelliteGuys.us (No hacking questions permitted!). You can also check out the website for White Springs TV, an FTA service.

WARNING: There have been reports of crooked dealers selling counterfeit versions of the popular Pansat brand receiver boxes. Make sure you by from a recommended dealer.

A “peoples network” consisting of a Free-To-Air satellite channel feeding low-power stations and FTA dishes may be pricey, but can be done. There are a number of religious and ethnic services, as well as a few “family entertainment” services, already on satellite. There are also a number of FTA services that are run by expatriate citizens of other countries, such as “Tapesh TV” and “Simay Azadi” which are based in the USA but serve viewers in Iran, often broadcasting news and information that may be censored by the viewer’s government. To contradict Gil Scott-Heron; The revolution might very well be televised, but it probably won’t be on cable.

Original Guerrilla Television
There are a number of outlaw radio projects going on around the country. Less frequent, but just as feasible, is a people’s television network. Presently there are three basic types of TV systems: Broadcast, which is the sending of signals directly from a station’s transmitter to home receiver sets; Cable, where the cable company employees extremely sensitive antenna to pick up broadcast transmissions and relay them and/or they originate and send them; and thirdly, Closed Circuit TV, such as the surveillance cameras in supermarkets, banks and apartment house lobbies.

The third system as used by the police is of little concern, unless we are interested in not being photographed. The cameras can be temporarily knocked out of commission by flashing a bright light (flashbulb, cigarette lighter, etc.) directly in front of its lens. For our own purposes, closed-circuit TV can be employed for broadcasting rallies, rock concerts or teach-ins to other locations. The equipment is not that expensive to rent and easy to operate. Just contact the largest television or electronics store in your area and ask about it. There are also closed-circuit and cable systems that work in harmony to broadcast special shows to campuses and other institutions. Many new systems are being developed and will be in operation soon.

Cable systems as such are in use only in a relatively few areas. They can be tapped either at the source or at any point along the cable by an engineer freak who knows what to do. The source is the best spot, since all the amplification and distribution equipment of the system is available at that point. Tapping along the cable itself can be a lot hairier, but more frustrating for the company when they try to trace you down.

Standard broadcasting that is received on almost all living room sets works on an RF (radio frequency) signal sent out on various frequencies which correspond to the channels on the tuner. In no area of the country are all these channels used. This raises important political questions as to why people do not have the right to broadcast on unused channels. By getting hold of a TV camera (Sony and Panasonic are the best for the price) that has an RF output, you can send pictures to a TV set simply by placing the camera cable on or near the antenna of the receiver set. When the set is operating on the same channel as the camera, it will show what the camera sees. Used video tape recorders such as the Sony CV series that record and play back audio and video information are becoming more available. These too can be easily adapted to send RF signals the same as a live camera.

Whether or not the program to be broadcasted is live or on tape, there are three steps to be taken in order to establish a people’s TV network. First, you must convert the video and audio signals to an RF frequency modulated (FM) signal corresponding to the desired broadcast channel. We suggest for political and technical reasons that you pick one of the unused channels in your area to begin experimenting. The commercial stations have an extremely powerful signal and can usually override your small output. Given time and experience you might want to go into direct competition with the big boys on their own channel. It is entirely possible, say in a 10 to 20 block radius, to interrupt a presidential press-conference with more important news. Electronic companies, such as Jerrold Electronics Corp., 4th and Walnut Sts., Philadelphia, Pa., make equipment that can RF both video and audio information onto specific channels. The device you’d be interested in is called a cable driver or RF modulator.

When the signal is in the RF state, it is already possible to broadcast very short distances. The second step is to amplify the signal so it will reach as far as possible. A linear amplifier of the proper frequency is required for this job. The stronger the amplifier the farther and more powerful the signal. A 10-watt job will cover approximately 5 miles (line of sight) in area. Linear amplifiers are not that easily available, but they can be constructed with some electrical engineering knowledge.

The third step is the antenna, which if the whole system is to be mobile to avoid detection, is going to involve some experimentation and possible camouflage. Two things to keep in mind about an antenna are that it should be what is technically referred to as a “di-pole” antenna (see diagram) and since TV signals travel on line of sight, it is important to place the antenna as high as possible. Although it hasn’t been done in practice, it certainly is possible to reflect pirate signals off an make equipment that can RF both video and audio existing antenna of a commercial network. This requires a full knowledge of broadcasting; however, any amateur can rig up an antenna, attach it to a helium balloon and get it plenty high. For most, the roof of a tall building will suffice. If you’re really uptight about your operation, the antenna can be hidden with a fake cardboard chimney.

We realize becoming TV guerrillas is not everyone’s trip, but a small band with a few grand can indeed pull it off. There are a lot of technical freaks hanging around recording studios, guitar shops, hi-fi stores and engineering schools that can be turned on to the project. By showing them the guidelines laid out here, they can help you assemble and build various components that are difficult to purchase (i.e., the linear amplifier). Naturally, by building some of the components, the cost of the operation is kept way down. Equipment can be purchased in selective electronics stores. You’ll need a camera, VTR, RF modulator, linear amplifier and antenna. Also a generator, voltage regulator and an alternator if you want the station to be mobile. One of the best sources of information on both television and radio broadcasting is the Radio Amateur’s Handbook published by the American Radio Relay League, Newington, Conn. 06611 and available for $4.50. The handbook gives a complete course in electronics and the latest information on all techniques and equipment related to broadcasting. Back issues have easy to read do-it-yourself TV transmitter diagrams and instructions. Also available is a publication called Radical Software, put out by Raindance Corp., 24 E. 22nd St., New York, N.Y., with the latest info on all types of alternative communications.

“Since the haphazard inception of this page, I have received well over 1000 emails from various folks in all corners of the earth, asking questions, seeking information or advice and offering tidbits of useful knowledge that all contribute to the success of this page. At it’s peak there were more than 10,000 hits per day. I was completely surprised at the substantial interest for Do-It-Yourself antennas that was present in the network community. Thanks to you all.

I did not devise the term “Cantenna”, but to the best of my knowledge, I did build the first one using the popular brand potato crisp can. I’ve adopted the use of the word simply because it’s appropriate. Thank you to the many folks who simultaneously discovered this word.

Interference, Health and Security Concerns
I’d like to say a little bit about Electromagnetic Waves. I’m sure you are eager to build an antenna or two for your 802.11b wireless network. Before you do anything else, it is important to think carefully about all the possible consequences of what you are doing. Simply put, you are going to be sending electromagnetic waves through the air. This can cause much distress to folks who are not expecting it, and when they get upset, they will call the FCC. So, you may want be knowledgeable about what you are doing before you do it. A few terms you should be familiar with are Radio Frequency Interference, Electro Magnetic Interference and Bandwidth Saturation.

It has been mentioned in this article that it is not legal to attach a non FCC-approved antenna to a wireless device. I suggest you read the FCC rules and regulations before doing anything. Seattle Wireless has a good collection. The antenna design I illustrate below is extremely experimental. I have heard that it’s use could cause interference in near-band frequencies that are commonly used in things such as portable wireless (not cellular) phones that people may have in their homes near you. There are all kinds of wireless devices out there that operate around the same band as 802.11b, and these are potentially disrupted by use of the equipment described here.

You may consider purchasing an SWR meter and you may exercise much care, consideration and caution for others if and when you decide you need an RF amplifier for use with your antenna. For most applications you will not need one. I have also heard that if your antenna is too efficient, that you may even damage your 802.11b device with too much current/feedback. If you do not know what you are doing, study until you are confident that you will not break people, places or things when you start experimenting. I am providing this information for the sake of information and I am not liable for any damages, injuries or other accidental or intentional harm caused by the use of it. Play nice. We are all in this together.

As if this was not yet enough to keep you from messing around with fast flying electrons, I have received many emails from folks who are very involved with HAM radio and other professions and hobbies that involve work with high frequency microwave radiation. They warn that 2.4 GHz just happens to also be the resonant frequency of plain old water. This is why a microwave oven works. The energy of an 802.11b device is the same kind of energy that cooks your food, but on a much smaller scale. This is important considering that we as humans are 98% made of water. I have been warned that exposure to even as little as a 1/4 watt amplified with a 14db antenna, such as described here, could lead to severe vision problems and possibly other health issues.

I like the idea of using wireless to do cool stuff. It’s really nifty. It’s not very secure though. Nothing really is “secure”. But wireless is even less so, because it is wireless. It does not require some guy breaking in to your home/business and tapping a physical connection for them to see the data you are sending. It’s flowing freely through the air, like the sound from you stereo speakers. If someone was standing outside your house, and you were rockin’ out with your stereo up loud, they could hear it as well.”

Wireless enthusiasts have been repurposing satellite dishes for a couple years now. This summer the longest link ever was established over 125 miles using old 12 foot and 10 foot satellite dishes. A dish that big is usually overkill for most people and modern mini-dishes work just as well. The dish helps focus the radio waves onto a directional antenna feed. We’re building a biquad antenna feed because it offers very good performance and is pretty forgiving when it comes to assembly errors. Follow along as we assemble the feed, attach it to a DirecTV dish and test out its performance. Why? With just a handful of cheap parts, a salvaged DirecTV dish and a little soldering, we were able to detect access points from over 8 miles away. Using consumer WiFi gear we picked up over 18 APs in an area with only 1 house per square mile.

Building the antenna
Biquad antennas can be built from common materials, which is nice because you don’t have to scrounge around for the perfectly-sized soup can. We did have to buy some specialized parts before getting started though. The most important part here is the small silver panel mount N-connector in the center of the picture; the entire antenna will be built on this. We purchased it from S.M. Electronics, part# 1113-000-N331-011. The “N-connector” is standard across the majority of commercial antennas and you can connect them to your wireless devices using “pigtails.” The longer pigtail in the picture is a RP-TNC to N-Male pigtail that we’ll use to connect our antenna to a Linksys WRT54G access point. The short pigtail is a RP-MMCX to N-Male pigtail so we can connect to our Senao 2511CD PLUS EXT2 WiFi card which is pictured. We also purchased 10 feet of WBC 400 coax cable so we wouldn’t have to sit with the dish in our lap. We got our surplus DirecTV dish from Freecycle. We’ll cover the reason for the mini butane torch later.

Trevor Marshall built one of the first biquad WiFi antennas found on the internet. We followed the slightly more thorough instructions found at martybugs.net. Here are the raw materials we started with: The wire is standard solid-core 3-conductor wire used for most house wiring. We didn’t have any copper printed circuit board material laying around so we used this thin sheet of copper and supported it using the 1/4-inch thick black plastic pictured.

The first step in building the element was stripping and cutting a 244mm length of wire. We marked the wire every 31mm with a permanent marker and began bending the wire into a double diamond shape. We tried to make the length of each leg 30.5mm. The easiest way to make really sharp bends in the solid copper wire is to use two pairs of pliers. With the pliers held perpendicular to each other bend the wire against one of the sets of jaws. Next we cut out a 110mm square of black plastic to use as a base for the reflector. We drilled a hole in the center to clear our connector. We then soldered a piece of copper wire to the center pin of our N-connector.

Next we soldered a piece of of wire to the outside of the connector. We ran into some trouble here. Our cheapy iron was not capable of getting the connector’s base hot enough to make a good solder joint. We bought a butane torch and used that to heat up the surfaces. This worked pretty well except it desoldered our center pin. We recommend you solder the outside piece of wire first before doing the center one. After the connector had cooled it was attached to the black plastic base using epoxy. The thin copper sheet was attached to the front with epoxy and trimmed to fit.

We let the epoxy cure for a while before proceeding. The next step was to solder our bow tie shaped element to the vertical wires. The element was supported by two pieces of scrap copper trimmed to 15mm to ensure proper positioning. Then the extra wire was trimmed off and the outside wire was soldered to the ground plane to complete the antenna. To make mounting to the dish easy we modified the original feedhorn. After removing the housing, internal components and shortening the feedhorn looked like this.

The antenna is attached by inserting the N-connector into the tube and then connecting the coax cable. Since the satellite dish has an off-center feed it looks like it is pointed at the ground when it is level with the horizon. Even though there are no angle markings for setting the dish at 0 degrees inclination we can still ensure that the dish is pointing at the horizon by setting the dish angle to 45 degrees and mounting it on a tube with a 45 degree angle.

Test results
The Engadget Corn Belt Testing Facility has broadband access provided by a local WISP. So we knew if we plugged in our antenna we were sure to pick up something in the area. We pointed the dish at the closest grain elevator, where the WISP mounts their antennas. We connected the dish feed to our Senao card and started up Kismet.

We expected to get one AP, but five is even better. Looking through the info strings we were able to determine where the APs were since the WISP had named them according to the town they are in. The AP on channel 5 is the one we pointed at in town A, 2.4 miles away. The AP on channel 6 is located in town B, 8.2 miles away. The two APs on channel 1 are a bridge between town A and town C which is located 2.6 miles directly behind the dish.

Our next test was to hook our WRT54G up to the dish and point it at a hill 1 mile away. We drove to the top of the hill and used an omnidirectional mini whip antenna with our Senao card to detect it. Our router was picked up easily. The found 14 other WISP APs including town D, 7.8 miles away. The WISP is definitely using some high powered equipment if we’re just picking this up with an omnidirectional antenna. For a final test we put the dish on the roof rack and parked on top of the hill to see if we could pick up any more APs. Our final count is 18 APs, 17 of those belonging to the WISP. This was a pretty fun project and shows that you can build decent wireless solutions using consumer gear.

For the curious: The WISP gives its subscribers a patch antenna with a built in power-over-ethernet access point. Once the antenna is mounted to the roof they run a single ethernet cable into the house which means they don’t have to worry about signal loss from coax. These client boxes are manufactured by Tranzeo.

Primestar was recently purchased by Direct TV who is phasing out all the Primestar equipment. This means that the dishes are being trashed, and are available for other uses such as the one I describe here. It is easy to make a surplus Primestar dish into a highly directional antenna for the very popular IEEE 802.11 wireless networking. The resulting antenna has about 22 db of gain, and is fed with 50 ohm coaxial cable. Usually LMR400 or 9913 low loss cable is used if the source is more than a few feet from the antenna. The range using two of these antennas with a line of sight path is around 10 miles at full bandwidth. I must stress the line of sight part though. Leaves really attenuate the signal.

Things You Will Need:
1. A Primestar dish. (You may use any old dish, but if it is bigger than the Primestar the gain will be higher, and it may not be within the Federal Communications Commission rules for use within the United States. In fact I have come to find out that there seem to be several different dishes that Primestar used, and I am only sure that the one I used, pictured above, used with the ordinary Wavelan or Airport transceiver card is within the effective radiated power limits given by the FCC.)
2. A juice can (about 4 inches in diameter and at least 8 inches long).
3. A chassis mount N connector.
4. You will also need a “pigtail” connector which has the proprietary Lucent connector (for the PCMCIA card) on one end and an N connector on the other. The pigtail can be obtained from a number of online stores for $35 to $40.

Use the Feed Can By Itself
You can use the feed can by itself as a cheap antenna. It works as well as the commercially available “range extender” antenna, but only in one direction, and it is so easy to construct!

IEEE 802.11a
This antenna modification is for the IEEE 802.11b networking protocol that operates at 2.4 GHz. It can be scaled easily to the 5 GHz frequency used by IEEE 802.11a by simply scaling the dimensions on the feed can and the excitation antenna to 2.4/5 = 48% of the dimensions shown above.

Parabolic cookers have been used for centuries now. The idea to concentrate light using curved mirrors was developed by the Greeks, Aztecs, Incas, Romans and Chinese. The Incas used bronze and gold for their mirrors and they built structures that were several stories high. This technology seems to have appeared around the same time for each of the civilizations. It is thought that Archimedes harnessed the technologyW to defend Syracuse from invading Roman fleets in 212 BC.

My Parabolic Solar Cooker
At first, I was open to anything to construct the solar cooker. I was thinking about constructing my paraboloid out of cobb and then sticking small pieces of glass into it as I’ve seen others do. However, it takes a lot of time to collect the cobb materials and build a paraboloid out of it, let alone one whose focus was accurate. A donated dish was viable, but would not have the heat capacity I was going for, so I set out to find another dish. While rummaging around Arcata Scrap and Salvage one day, I came across an old mesh satellite dish and I knew I had found my cooker. My mentor Bart Orlando and I hauled it to the Bike Library where my cooker began to take shape.

Location and Help
Most of the construction and testing took place at the Arcata Bike Library with the help of Bart Orlando. However, I did most of the cutting of the sheet metal at the HSU sculpture lab. We also used the pedal-powered tools there to construct the mount hot plate grill.

Method
The basic idea was to use a satellite dish and rivet sheet aluminum to it. This is because a satellite dish is already a paraboloid shape with a fairly exact focus. The sheet aluminum was to be cut into triangular pieces and then drilled in 3-5 places for the rivets. They would conform to the shape of the paraboloid and not lessen the integrity of the focal point. We wanted the aluminum to be as exact as possible to ensure that it would reflect enough light to fry some potatoes. I wanted to do more than boil water with my cooker.

The hot plate grill was to be constructed out of conduit and bike rims. We would flatten the ends of the conduit for easier attachment to the center pipe and rims, and then bolt it all together. We decided that a gimble would be the best for this project, so that we could move the pan (or pot) in any direction necessary to receive optimal sunlight. This is a more difficult design, but it gives the dish more freedom and a higher heating capacity.

We began the project by testing a dish that Bart had at the Bike Library. It was slightly oblong and wasn’t concave much, so we decided to test how accurate the focus was. I taped a few pieces of mylar on it and Bart and I took it out into the sun. It turned out that the dish had many foci because of its’ oblong shape. I had to set out to find another dish if I wanted to be able to fry food with it. The one we had just wasn’t going to cut it. That’s when I made a trip to Arcata Scrap and Salvage and found the perfect dish for my project.
can you see the light reflecting on my hand?

Final Construction
We started by disassembling the focal point of the dish. There was an awkward pole sticking out of the center which was not appropriate for the design we were going for. We got a grinder out and sawed through the metal so that we could manipulate the pipe into a hot plate grill. Since the pole was bent near the base, we figured that it might not work for our design specifics. Luckily, we found that we could remove the pole by loosening a bolt at the base, and that allowed for it to slide right out. We were able to locate a longer pole later on, but at the time, we were planning on using the one that came with the dish. We also had to remove a bunch of miscellaneous pipes and widgets sticking out the back side of the dish. They were things that helped keep the dish balanced in place but were not needed in our design. After that, the dish was ready to for transformation.
Sawing off the old mount pole.

The Hot Plate Grill
The next step was to construct a hot plate grill. The original focal point was somewhere between 27-31″ but we forgot exactly. In order to make the mount, we needed to know how long to make it, so I decided to find the theoretical focus by using the formula: x2 = 4 * p * y. It worked out to be 29 3/4″. We decided that it would be best if we used conduit to form a “v” shape and then fit in a few bike rims for the hot plate. We had to flatten the ends of the conduit and make sure that they were the right angle for the focus. This was done using a clamp and we were able to bend both pieces of conduit at the same time. The conduit pipes were a little too long so we had to shorten them using a Sawz-All at the Bike Library. After the sizing, it was time to drill some holes using a pedal powered drill press. We discovered that the center pipe we wanted to use was slightly shorter than we wanted, but being that we were in such a resourceful area, we rummaged around and found a pipe that was the perfect size and width. The next step was to drill holes in the flattened sides of the conduit and our newly-found pipe and fit the pieces together. They fit quite nicely. We had to make sure that both the conduit pipes were bent at the same angle or else the structure would be unstable. The next step was to drill holes in the bike rim so that we could bolt it to the mount structure we just created. We drilled the holes using a drill press at the HSU sculpture lab and it was ready to be bolted together.

The Mirror Finish
Bart had acquired a bunch of sheet metal that he had wanted to use on a previous project, but decided that my dish could use them. There wasn’t quite enough cut pieces to cover the entire surface area of the dish and I had to take some scrap sheet aluminum to the HSU sculpture lab to cut them into triangular shapes. After they had been cut, they needed to be prepared for riveting. It took about a half an hour to drill holes in all of the pieces and they were quickly ready to be fastened to the dish. While putting the pieces in place, we noticed that the holes we had drilled did not always match the pattern of the mesh, and there were areas where the mesh was covered with pieces of solid metal. These areas had to be dealt with differently. In some areas, we were able to drill holes through the metal for the rivets, and in others, we devised a way of using a thin wire to attach the pieces. I used a paperclip I found on the ground and stuck it through the hole and then through the mesh slightly above the triangle. Using pliers, I twisted the ends of the paperclip to form a tight grasp on the metal; it worked quite well. I was also able to get rivets with a larger gripping range and that helped with the thicker areas. After the pieces were all riveted into place, we noticed that there was a gap – there wasn’t quite enough sheet metal to cover the whole dish. I drilled some more holes in the scrap pieces I had and was able to fasten them to the dish. There’s still a little gap, but that really won’t matter since the dish is so big, and most of it is coated anyway. The last step was to buff the aluminum to a sweet finish.

The Final Product
Now the dish is ready for cookin’. It could use a little shining up with some Citra-Sol or something of that nature, but even without a shine job, the focus gets pretty hot. In terms of setting the dish up, all we need is to lean it up on something. There’s a mount on the back of it with the capability of being staked in the ground. For that, I would have to find a long piece of pipe about 3 1/2″ in diameter and at least 1/4″ thick.

Testing
My solar cooker is spectacular for cooking veggie burgers and beans. At 1:00 pm, the dish heats up to 400 oF. Around 2:00-3:00 pm, the dish heats up to 350 oF. I’ve found that the cooker doesn’t burn food too easily. When I’ve forgotten abut something that’s cooking, the sun moves in the sky. That automatically reduces the heat at the focus. Things have gotten caramelized, but it’s hard to burn something.

Everything else we had lying around at the bike library and was free (i.e. nuts & bolts, bike rims, pipes, tools). Bart gave me sheet metal that he was going to use for a different dish so that I could make mine.

Conclusions
The first time you construct a solar cooker, you learn a lot in terms of what methods and materials to incorporate in construction. The next cooker I make will probably be a lot easier since I’ve already been through it. Next time, I would like to use a lighter aluminum for the mirror finish. The dish is relatively light for it’s size, but it’s certainly difficult to handle on your own. I would also consider a dish without reinforcing structures. They got in the way when I was riveting, and as unable to attach the aluminum in some areas. In order to be exact, the mirror finish needs to coat the entire surface area of the dish. This increases the heat capacity. But considering my dish’s size, I don’t think that it will have a hard time reaching high temperatures. And it hasn’t. I’ve been cooking lunch with it for the past few days now, without a shine job on the sheet aluminum.

Discussion
This project was the coolest thing I’ve done all year. Cooking food with my solar cooker is the best feeling in the world. It’s cool to see something that I created work so well. The thing that I would like to add is a mount pole for the back of the dish. I am able to lean it up against a chair and stuff like that, but if i have to put it up at a hard angle, I might have a little more trouble. So that’s something I’ll have to think about, but for now, I’m having a blast in the afternoons cooking gardenburgers and fried potatoes.

Things to Keep in Mind/Common Errors to Avoid
* Watch out for stray rays of light that come off your cooker. They could possibly start a fire if you aren’t careful. It isn’t much of a worry if your dish is more concave, but the flatter the dish is, the more likely that you will have stray rays of light.
* Wear sunglasses when cooking because it gets really bright and hard for your eyes to handle.
* Use a cast-iron or some other type of black cooking pot/pan. Any other color might reflect the light and that’s not what you want. The black absorbs the light and brings the temperature up in the pot/pan.

US: The Washington-based Intelsat gave a firm assurance yesterday that it would take all possible steps to stop the Liberation Tigers of Tamil Eelam (LTTE) from illegally broadcasting its propaganda over their satellites. “Intelsat does not tolerate terrorists operating illegally on it satellites. Since we first learned of the LTTE’s signal piracy, we have been actively pursuing a number of technical alternatives to halt the transmissions. We are clear in our resolve to ending this terrorist organisation’s unauthorised use of our satellite,” Intelsat, the world’s largest provider of fixed satellite services, said in a statement.

The announcement came after Intelsat officials and technical experts met Sri Lanka’s Ambassador to the United States Bernard Goonetilleke on Tuesday to discuss the steps Intelsat was taking to address the unauthorised use of one of its satellites by the LTTE. “We have been actively pursuing avenues to terminate the illegal usage of our satellite,” Intelsat spokesman Nick Mitsis said.

In a telephone interview, Intelsat’s Executive Vice President and General Counsel Phillip Spector told this correspondent that his corporation would do “every possible thing to turn off the LTTE (sponsored national Television of Tamil Eelam and Voice of the Tigers radio programme) as soon as possible” from their satellite. Spector maintained the position of the corporation that the LTTE was pirating an empty transponder frequency of their Satellite 12 for the broadcasts. He said it was actually stealing the space of the satellite and called it piracy.

Asked whether al-Qaeda could use the same satellite for the purpose of an attack against the United States, Spector said it was only a hypothetical situation. But when pressed for an answer, Spector said it was technically possible. Spector said no customer is authorised to sell their frequency to anybody else and maintained it was an empty space the LTTE was using. Spector denied earlier published newspaper reports that Intelsat has done business with Hezbollah, another terrorist group, and insisted “Not in my time”.

While refusing to give a date for turning off the LTTE, the Intelsat lawyer said “if you understand the satellite technology it is quite a complex task and it will be done as soon as possible”. Intelsat said: “Intelsat, the leading provider of global satellite communications, today issued a statement with regard to the unauthorised use of one of its satellites by the Liberation Tigers of Tamil Eelam (LTTE). The US State Department lists the LTTE as a foreign terrorist organisation. The Sri Lanka Embassy and Intelsat agree that these illegal transmissions by the LTTE are a violation of Sri Lankan and US laws. Following the discussion, Ambassador Goonetilleke said: “I am satisfied that Intelsat is taking these unauthorised transmissions very seriously, and believe it would do all that it can to stop the terrorist transmissions. I am confident that Intelsat will continue to cooperate with Sri Lankan authorities in this matter.” The issue was also taken up by Sri Lanka at a meeting of the International Telecommunications Satellite Organisation in Paris last month, Sri Lankan officials said.

The Chinese government is furious over a rare but successful case of satellite signal hijacking in which TV signals from the Sinosat-1 satellite were temporarily overridden and replaced with programming promoting the outlawed Falun Gong cult. According to an official Sinosat statement released 8 July, a series of signal hijacks occurred between 23 June and 30 June, attacking Sinosat’s 2A and 3A transponders, which provide TV signals to rural villages in China via an earth station in Yungang, which reported that all of state TV broadcaster CCTV’s nine channels, as well as 10 provincial channels, had been hijacked by “unidentified signals … of similar frequency spectrum with that of the CCTV programs”. Minutes after monitor screens went black, Sinosat says, “Falun Gong propaganda materials appeared on screen; and … the word `Falun Gong’ in Chinese flashed again on the screen”. The Chinese government–which outlawed the Falun Gong as an “evil cult” in 1999, and also puts a premium on strict media control–has predictably condemned the hijackings, and has vowed to hunt down and punish those responsible. One obstacle Chinese officials face in that regard is whether the hijackers are even within China’s legal jurisdiction. The Ministry of information Industry has accused–but not publicly identified–overseas parties of helping to plan the interruption.

Hijacking Sinosat signals from outside the country is possible since Sinosat’s footprint extends well outside China’s borders, to include the Indo-Chinese peninsula, Indonesia and the Philippines. Satellite experts say that overriding a satellite signal requires a satellite dish transceiver a minimum of three meters wide and with a transmission power well beyond the capabilities of off-the-shelf consumer gear. Hijackers would either have to commandeer an earth station facility or get hold of an industrial-grade dish that can be moved around and hidden. This is why jamming satellite signals is often the province of military organizations and disgruntled earth station employees rather than independent groups.

However, it wouldn’t be the first time Falun Gong members have interrupted regular TV programming in China. In April, Chinese officials arrested nine Falun Gong members for hacking into a Chinese cable TV system on 5 March in the northeastern city of Changchun, where they allegedly cut off TV signals and used home-made broadcasting equipment to air their own programs. And that was one of seven reported cable-TV hacks during the first half of this year, according to the group’s Falun Dafa Information Center, which confirmed the activity in a 28 June editorial–five days after the first satellite signal hijacking was reported.

Britain’s Ministry of Defense is denying that the nation’s military satellites were hacked, but the reported disruption raises questions about the security of all satellite-based communications services. Control of one of the satellites in Britain’s Skynet system, which delivers communications services to the nation’s Royal Air Force and other armed forces units, was reportedly seized by hackers over the weekend. The British government was then the subject of an alleged blackmail threat following the attack.

But the government is denying that the James Bond-like incident ever occurred. “The satellite system has not been hacked into and the satellite has not changed course,” said a spokeswoman for Britain’s Ministry of Defense, who declined to give her name. “And, the security levels make it extremely difficult, if not impossible, to hack into the system.” Industry experts said hacking into a satellite system is difficult, and commercial satellites are relatively safe from meddlers. Yet as the communications industry begins to rely more heavily upon satellites, the cause for concern over hackers is no longer limited to Webmasters.

Commercial satellite launches are on the rise and the number of “birds” in the sky continues to grow. There are about 330 commercial satellites in orbit today, according to the Satellite Industry Association, a commercial trade group. Companies such as Iridium, a satellite mobile phone provider which owns a 66-satellite network, and Teledesic, a satellite data provider, have hinged their whole business success on their galactic machinery. Meanwhile, direct broadcast satellite operators, such as DirecTV and EchoStar Communications, have grown in popularity in recent years and, as a result, have cut into the cable television market.

This increasing use of satellites raises security and reliability questions should computer hackers turn their attention to the heavens. Although not the work of hackers, nearly 40 million paging customers were without service last year when PanAmSat’s Galaxy IV satellite broke down–a reminder of what could happen when a communications satellite fails. “[Hacking is] a concern and companies are taking steps to prevent that,” said Clayton Mowry, executive director of the Satellite Industry Association. “But it’s not like you’d use a backyard dish to do this.” Industry experts said satellite companies use encryption to protect their data and company control centers, used to monitor satellites and maintain their correct position in space, are typically secure facilities with surveillance cameras, alarms, and other security measures. “You’d need the encryption keys, or access to a control center, or both,” Mowry said. “I don’t know of any cases where satellites have been commandeered.”

How to hack
Analysts said there are several ways satellite systems can be disrupted. With sufficient power from a satellite dish on the ground, an orbiting satellite’s signal can be blocked. “One way is simply brute force, by sending a signal up to a given satellite and jamming it,” said Steve Blum, president of Tellus Venture Associates, a satellite consulting firm. “That’s nothing new. That’s as old as radio itself.”

Experts said that occasionally happens by accident, but jamming a satellite is easy to trace and communications services, such as TV signals, are rarely disrupted as programmers and providers usually have backup capacity on other satellites. The computer systems used to monitor and control the satellites also pose a potential weak link; although most are housed in secure facilities, in theory they could be infiltrated, Blum said.

But industry sources said many of the potential pitfalls are not unique to satellites. Smaller radio stations have been known to have their signals blocked by more powerful transmitters. And hackers could just as easily attempt to break into the computer systems of a cable operator in an attempt to shut down services to a certain neighborhood. “The guys that designed these systems all have military histories,” Blum said. “You’re dealing with companies that are very much knowledgeable about security.”

Every time a thruster is fired, propellant is used. Once the supply of propellant is exhausted, the satellite cannot be maintained at proper position and attitude, and the satellite must be retired. Propellant capacity is the primary factor which determines the useful life of a communications satellite. It is easy to understand that a primary goal of every satellite owner is the conservation of propellant. Many computer studies have been done to determine the optimum trade-off between satellite stability and propellant usage. These studies have shown that a substantial majority of the propellant is used for just one stationkeeping function: keeping the satellite from drifting along its north-south axis. Kent Carson, director of advanced programs for Comsat Systems Division, has stated that between 80% and 90% of the propellant is used for this function alone. [1]

Economics Of Inclined Orbits
From the point of view of a satellite owner, the economics of this situation are compelling. On one hand, the revenue derived from leasing transponder time on an inclined-orbit satellite is considerably less than the revenue which could be realized from a truly geostationary satellite. On the other hand, propellent usage is cut dramatically, thereby extending the useful life of the satellite, often by several years. The potential revenue to be derived from this extended life more than offsets the revenue lost through reduced transponder pricing. It comes as no surprise, then, that many satellite owners have allowed their geostationary satellites to drift into inclined orbits.

If only cars could last so long. This month, a satellite resembling a shiny spinning drum and orbiting 21,156 miles above Earth celebrated its 41st birthday, astounding engineers and scientists, some of them the children of those who built it.

For years, the satellite has served as an emergency communications link for rescue operations, including the 1985 Mexico City earthquake and the 1980 Mt. St. Helens volcanic eruption. It was supposed to live for only three years when it was launched in 1967. That’s when Lyndon B. Johnson was president and bell-bottom pants were the rage. But the spacecraft, known as ATS 3, isn’t alone. Many satellites are operating well past their life expectancy, so much so that manufacturers are hurting from lack of demand for new, replacement satellites.

And those who are buying are asking for guarantees that the new satellites, which can cost as much as $300 million each, will last two to three times as long as the early birds. “It’s a mixed blessing,” said John S. Edwards, a space industry analyst for Forecast International. “It says great things about your product, but the satellite-making business is floundering because there are hardly any sales.”

Engineers at Boeing Co.’s sprawling satellite-making plant in El Segundo know about the sales drought only too well. Of the 245 Boeing satellites that have been launched into service, 166 have exceeded their design life. That’s more than two-thirds of the spacecraft built at the facility since the 1960s. A third of all satellites have lasted at least twice as long as expected. That has been the bane of the sales department. With the telecom bust early this decade and consolidation in the satellite services industry, Boeing has sold only one commercial satellite this year. In the late-1990s boom years, it was tallying a dozen orders annually.

Some satellites are living longer because the initial estimates of their longevity were conservative, but many have operated well beyond even the wildest expectations. “In designing them, we had to take into account all the worst-case scenarios,” said Art Rosales, Boeing’s director of commercial and civil satellite services and a 29-year veteran of the satellite business. Because most satellites can’t be repaired once they’re in space, every contingency was considered. “The worst cases didn’t happen, and that has translated to longer life,” he said.

40. What Is An Inclined Orbit Satellite And How Can I Receive Them?
Inclined orbit birds are satellites that “wobble” north and south of the
vary in the vertical plane, as explained in the previous paragraph. At
the end of a satellite’s life, when station keeping fuel is running low
if a replacement satellite is not ready, there is the option to “go
inclined”. One method used is called the “Comsat Maneuver”, which puts
the bird into an elongated figure 8 pattern. On C band this method can
get 6 months or more of life out of a near dead satellite (Usually the
electronics are fine, it is just the low amount of Hydrazine fuel that
marks the EOL or End Of Life of a satellite. On C band a slightly
inclined satellite will appear to have a weaker signal during parts of the
day when it is off axis. Many of us remember that this was done with the
old Telstar 301, causing some of the Wild and Network feeds to be less than
perfect. However, it is better than no satellite at all, which is the
case when a launched bird BLOWS UP like Telstar 402 did in late 1994, meaning
that 302 will go inclined while waiting for T-402R. In addition to these
situations, there are birds that are kept in inclined orbits for YEARS.
Several Intelsats are this way, as are a couple of SBS birds, such as
SBS3. ON KU band, because of narrower beamwidth, an inclined bird can
only be viewed during an hour or so a day on a standard satellite system,
when its wobble places it directly over the equator. The Robert Smathers
SSSSC Chart lists the times of day you can pick up these inclined birds.
Some, like SBS3 have a continuous ID slate so you can find them.
Professional Downlinkers often have DUAL AXIS tracking systems which allow
for adjustment in the vertical as well as horizontal plane. In 1995, NBC
will move its feeds off K2 and onto an inclined SBS bird. All NBC affiliates
will be outfitted with costly auto tracking systems. The good news is that
it is now possible for the HOME BACKYARD TVRO OWNER to install his own
system to track these inclined orbit birds. The key component of this
setup is a “vertical kit” which consists of a heavy steel “hinge” which
will allow your dish to move up and down. The cost for this kit is around
$70, and if you are a bit of a tinkerer, it is well worth the money. To this
kit, you simply add a positioner arm (you can do like I did and scrounge one
for very little money) and you will need a means of providing the 24 volt
DC current with switchable polarity. This can be accomplished by using
an old manual type dish positioner to control the vertical tracking. These
can be had free or very cheap. Such a system is NOT automatic, you need
to use your eyeballs and your IRD’s signal readout to peak the signal and
you need to adjust the tracking every 10 minutes or so. If you are chasing
newsfeeds, this won’t be too much bother. If you really get into tracking
inclined birds, there are computerized tracking systems, and even a few
IRD’s that have the ability to track them automatically. It depends on
your own tastes, desires, and level of technical expertise. The vertical
kit I purchased was from Global Communications (See Dealer list at end of
this article) Since he is a TVRO dish design engineer, he can quickly
determine if your system will adapt to this type of system. Hint: if you
have an AJAK H/H drive, the answer is YES! During the Olympics it was fun
to be able to watch the feeds LIVE and not have to wait for the USA delay
broadcasts. Many of these feeds were on an inclined Intelsat. Besides
NBC, activity on inclined birds is fairly sparse, mostly special feeds.
Thus the option of being able to track these satellites is not for everyone
but the option is certainly there for folks who do.

39. How Long Does A Satellite “Last” And Why Do They Get Regularly Replaced?
The average lifespan for a communications satellite is about 10 years. While
the electronics inside the satellite can last many many years, the
determining factor is the “station keeping fuel”. Satellites only “appear to
be stationary because of their location in the Clarke Belt, in reality they
are whirring about the planet, and their orbits become eccentric if left
alone. So each satellite has small rockets on board to regularly adjust
the orbit of the bird. After 10 years this fuel runs out, and the satellite
can no longer be adjusted with respect to its position. This causes the
satellite to start to appear to “wobble” up and down in the orbital plane,
and eventually become unusable. Before this happens, a replacement bird
is launched, and the old satellite is unceremoniously “kicked” up into a
higher “parking” orbit. While it is a nice thought that some day a
space salvage company could go up there and refuel all those old birds,
it is unlikely, and the rapid changes in technology make the older low
power satellites nothing more than curious antiques.

C-COM has developed a proprietary inclined orbit satellite tracking algorithm which will provide C-COM customers the ability to use inclined orbit satellites for their space segment needs. Inclined orbit satellites are end of life satellites that may have an additional useful life span from 6 month to a few years, however they are no longer in their prescribed controlled orbit due to lack of fuel.

From the point of view of a satellite owner, the economics of this situation are compelling. On one hand, the revenue derived from leasing transponder time on an inclined-orbit satellite is considerably less than the revenue which could be realized from a truly geostationary satellite. On the other hand, propellent usage is cut dramatically, thereby extending the useful life of the satellite, often by several years. The potential revenue to be derived from this extended life more than offsets the revenue lost through reduced transponder pricing. It comes as no surprise, then, that many satellite owners have allowed their geostationary satellites to drift into inclined irbits.

An inclined-orbit satellite poses a problem for the end user: the earth station antenna must track the satellite. For this purpose, the antenna must be equipped with a dual-axis steerable mount and a tracking controller. A dual-axis steerable mount is a motorized mount which can be moved independently about two axes: east-west and up-down. Those moves are program-controlled. This type of controller mathematically calculates the pointing angles to the satellite and moves the antenna accordingly. Calculations are based on program data entered into the controller.

This type of controller is capable of moving the antenna continuously, rather than in a series of steps. This technique is advantageous in low-signal situations where any change in AGC voltage would result in degraded signal quality. With this feature enabled, the iNetVu controller will ensure that the mobile antenna maintains its maximum peaked signal on the configured inclined orbit satellite irrespective of their inclination angle. They have decided to develop this proprietary inclined orbit application for iNetVu controllers based on demand from the customers. This added feature will provide existing and future customers with the ability to use any inclined orbit satellite, should there be one available to them, and take advantage of the lower cost space segment offered over these satellites.

The “Kessler Syndrome” is an orbital debris term that has become popular outside the professional orbital debris community without ever having a strict definition. The purpose of this writing is to clarify the intended definition, to put the implications into perspective after 30 years of research by the international scientific community, and to discuss what it may mean to future space operations.

Historical Background
As far as I am aware, the term originated with a colleague, John Gabbard, who worked for NORAD. NORAD maintained a catalogue of man-made objects in orbit, but did not maintain a breakup record of events in orbit. John unofficially kept a record of major satellite breakup events, which later proved very useful in understanding the sources of smaller orbital debris. John is known for his description of these events with a graph we now call a “Gabbard Plot”.

When I met John in 1978, I had just published the Journal of Geophysical Research (JGR) paper, “Collision Frequency of Artificial Satellites: The Creation of a Debris Belt”. This paper predicted that around the year 2000 the population of catalogued debris in orbit around the Earth would become so dense that catalogued objects would begin breaking up as a result of random collisions with other catalogued objects and become an important source of future debris. These finding were important for three reasons:
1. At the time, it was generally assumed that there were very few objects in orbit that were too small to catalogue, although there was no definition as to what limiting size was in the catalogue. The paper illustrated that even if this assumption were correct, future collisions between catalogued objects would produce a large amount of small debris fragments. This small debris population would be more hazardous to other spacecraft than the natural meteoroid environment immediately after the first collision.
2. Each collision would also produce several hundred objects large enough to catalogue, increasing the rate that future collision breakups would occur….resulting in an exponential growth in the collision rate and debris population.
3. The only way to prevent this exponential growth was to reduce the number of rocket bodies and non-operational spacecraft left in orbit after their useful lifetime.

It was the second prediction that caught John Gabbard’s attention. While talking to a reporter shortly after the publication of the JGR paper, John used the phrase “Kessler Syndrome” to summarize my prediction of a future cascading of collisions in orbit. The reporter published the phrase. Perhaps it was a 1982 Popular Science article that made the term more popular, since the Aviation and Space Writers Association gave the author, Jim Schefter, the 1982 National Journalism Award for the article. However, regardless of the source, the label stuck, becoming part of the storyline in some science fiction, and a three-word summary describing orbital debris issues.

However, not all who have used the phrase have referred to it in the context of its original meaning. It was never intended to mean that the cascading would occur over a period of time as short as days or months. Nor was it a prediction that the current environment was above some critical threshold…although the concept of a critical threshold was an important possibility that was studied in detail more than 10 years later. The “Kessler Syndrome” was meant to describe the phenomenon that random collisions between objects large enough to catalogue would produce a hazard to spacecraft from small debris that is greater than the natural meteoroid environment. In addition, because the random collision frequency is non-linear with debris accumulation rates, the phenomenon will eventually become the most important long-term source of debris, unless the accumulation rate of larger, non-operational objects (e.g., non-operational payloads and upper stage rocket bodies) in Earth orbit were significantly reduced. Based on past accumulation rates, the 1978 publication predicted that random collision would become an important debris source around the year 2000, with the rate of random collisions increasing rapidly after that, if the accumulation rate were not reduced to near zero.

Findings Since 1978
Combined with the discovery that 42% of the catalogued objects were the results of only 19 explosions in orbit of U.S. upper stage rockets and that NORAD was not tracking “all man-made objects” as generally believed, NASA took these findings and predictions seriously. Beginning in October of 1979, I was given funds to begin research for data to more accurately define the current and future debris hazard, and understand techniques to limit the future growth in the debris population. With these funds, we accomplished our objectives with a combination of modeling, measurements that sampled the environment, ground tests to simulate space collisions, and coordination with the space community to determine cost-effective techniques to minimize future growth of the debris population.

We sampled the small debris environment by developing and using ground telescopes and powerful, shorter wavelength radars. We also analyzed recovered spacecraft surfaces for impacts using scanning electronic microscopes, which allowed us to determine the chemistry of the objects causing those impacts. Together with the Air Force, we conducted hypervelocity ground simulation of collisions and examined ground explosion data to more accurately predict the amount of small debris generated. We also developed much more elaborate computer models which we used to test our assumptions and ground data against the data we obtained by sampling the environment. We used these computer models to test the effectiveness of various techniques to minimize future growth in the debris population. These efforts were lead by a team of scientists in what is now known as the NASA Orbital Debris Program Office. Other international governmental agencies participated in this research, forming an international organization now known as the Inter-Agency Space Debris Coordination Committee (IADC). The following conclusions were reached as a result of this research:
1. The hazard from the debris that was too small to catalogue had already exceeded the hazard from the natural meteoroid environment. The sources of that debris included not only explosions, but paint flecks from spacecraft surfaces, exhaust from solid rocket upper stages, and leaks of coolant from nuclear reactors.
2. Better data and more accurate modeling by NASA and the international community support the conclusion that the long-term threat to the environment is collision cascading, as predicted in 1978.
3. Modeling results supported by data from USAF tests, as well as by a number of independent scientists, have concluded that the current debris environment is “unstable”, or above a critical threshold, such that any attempt to achieve a growth-free small debris environment by eliminating sources of past debris will likely fail because fragments from future collisions will be generated faster than atmospheric drag will remove them.
4. Although the rate of growth in the catalogued population has been reduced as a result of new operational procedures that minimize the possibility of explosions in orbits and leaving non-operational upper stages and payload in orbit for periods longer than 25 years, the catalogued population continues to increase, but at a lower rate than it was increasing prior to the 1978 paper.

Significance of the “Kessler Syndrome” Today
On February 10, 2009 the Iridium 33 and Cosmos 2251 satellites collided with a velocity of ll.6 km/sec, at an altitude of 790 km. The collision was catastrophic, likely producing hundreds of fragments large enough to catastrophically breakup other satellites, and tens of thousands of fragments large enough to damage other satellites. This is the first clear example of what was predicted in 1978. Although there have been three other random collisions between catalogued objects since 1991, none of those were catastrophic.

Although all existing data and analysis support the major conclusions presented in the 1978 JGR paper, there are minor differences. The most obvious is the difference between the predicted growth rate in the catalogue population of 510 objects per year compared with the actual growth rate, which was less. There were a number of conditions that contributed to the lower rate: 1. The success of the orbital debris program in establishing international agreements that reduced the number of accidental explosions in orbit. These explosions had been a major source of catalogued debris. 2. An abnormally high solar activity increased the upper atmospheric density and caused more satellites to reenter. 3. The declining economy and eventual fall of the USSR significantly reduced the number of Soviet launches. As a result of these conditions, the actual average growth rate over the last 50 years was about 300 objects per year. This rate would have been lower, had it not been for the Chinese anti-satellite test in 2007, which produced over 2000 fragments large enough to catalogue. A rate of 300 objects per year is close to the lower assumed rate in the 1978 JGR paper. This average growth rate would predict the first collision between catalogued objects to have occurred around the year 2000, and it was assumed to be a catastrophic collision.

The lower growth rate of 320 objects per year in the 1978 paper predicted two collisions by 2009, both catastrophic. Although the actual number of collisions is too few to be statistically meaningful, they may indicate that the actual collision rate could be higher than predicted, but fewer are catastrophic. This higher collision rate would be consistent with the uncertainty in spacecraft area subject to collisions, as was noted in 1978. In 1991 and 2000 publications, the collision area was shown to be about 2.5 times greater than adopted in 1978. The 2000 publication also concluded that not all cataloged fragments were massive enough to cause a catastrophic collision…this would be especially true if the colliding fragment hit an antenna, stabilizer boom, or solar panel, or if the target were the empty tank of an upper stage. The presences of antennae, solar wings, and stabilizer booms were ignored in 1978, and obviously hitting one of these areas will only transfer a fraction of the impact energy to the entire spacecraft structure, reducing the likelihood of a catastrophic breakup. Also an impact into the empty fuel tank of an upper rocket stage may not transfer all the impact energy to the rocket body structure….again not causing a catastrophic breakup. We may have been lucky that only one of the four collisions since 1991 was catastrophic…or it may be that only one out of four of the collisions between catalogued objects will be catastrophic. The 1978 prediction of collision frequency becomes more consistent with the actual collision frequency by simply assuming that the area used in 1978 is the average catastrophic collision area, which was the intent of the paper. However, a more accurate understanding of both the non-catastrophic and catastrophic collision frequency is achieved by using data generated since 1978 in more accurate models currently used by the Orbital Debris Program Office.

Despite the absence of random catastrophic collisions, the predicted fluxes of smaller debris in 1990 and beyond in the JGR paper are not too different from what has been measured as a result of the orbital debris program. Accidental explosions and a few intentional collisions almost certainly contributed to the similarity…. and possibly some non-catastrophic collisions involving an un-catalogued object also contributed. However, the major contributors were a number of small debris sources that were discovered since 1978. Even though these sources have produced a debris environment in the past that is about the same as predicted from collisions, past debris sources are fundamentally different from future random collisions between catalogued objects. The past sources produce debris at a rate that is proportional to the number of objects in orbit, while the future frequency of collisions will produce debris at a rate that is proportional to the square of the number of objects in orbit. For example, if one were to double the number of upper stages and payloads in orbit, each having a probability that they would explode, then the rate that debris is generated by explosions would also double. However the rate that debris is generated by collisions between these objects would increase by a factor of four.

The 1978 prediction of a catastrophic collision between catalogued objects of 0.013 per year was based on a catalogue containing 3866 objects; today, the catalogue contains about 13,000 objects, or more than 3 times as many objects. This gives a collision rate that is more than 10 times what it was just over 30 years ago, or 0.13 per year….which is the same as one catastrophic collision between cataloged objects every 8 years….with the time between collisions rapidly becoming shorter as the catalog continues to grow. The larger fragments from either explosions or collisions will further accelerate the rate of collisions.

Most of the collisions in the 1978 paper were predicted to take place between 800 km and 1000 km altitude. That is even truer today. Not only is this region rapidly growing, certain altitudes contain a high concentrations of satellites, and the inclinations of their orbits are near polar, both conditions increasing the probability that they will collide, and do so with collision velocities that average more than 10 km/sec. We are entering a new era of debris control….an era that will be dominated by a slowly increasing number of random catastrophic collisions. These collisions will continue in the 800 km to 1000 km altitude regions, but will eventually spread to other regions. The control of future debris requires, at a minimum, that we not leave future payloads and rocket bodies in orbit after their useful life and might require that we plan launches to return some objects already in orbit.

These control measures will significantly increase the cost of debris control measures; but if we do not do them, we will increase the cost of future space activities even more. We might be tempted to put increasing amounts of shielding on all spacecraft to protect them and increase their life, or we might just accept shorter lifetimes for all spacecraft. However, neither option is acceptable: More shielding not only increases cost, but it also increases both the frequency of catastrophic collisions and the amount of debris generated when such a collision occurs. Accepting a shorter lifetime also increases cost, because it means that satellites must be replaced more often….with the failed satellites again increasing the catastrophic collision rate and producing larger amounts of debris.
Aggressive space activities without adequate safeguards could significantly shorten the time between collisions and produce an intolerable hazard to future spacecraft. Some of the most environmentally dangerous activities in space include large constellations such as those initially proposed by the Strategic Defense Initiative in the mid-1980s, large structures such as those considered in the late-1970s for building solar power stations in Earth orbit, and anti-satellite warfare using systems tested by the USSR, the U.S., and China over the past 30 years. Such aggressive activities could set up a situation where a single satellite failure could lead to cascading failures of many satellites in a period of time much shorter than years.

As is true for many environmental problems, the control of the orbital debris environment may initially be expensive, but failure to control leads to disaster in the long-term. Catastrophic collisions between catalogued objects in low Earth orbit are now an important environmental issue that will dominate the debris hazard to future spacecraft.

Satellites are usually insured against many different kinds of failure, beginning with their delivery to the launch pad, their ascent into orbit, and their in-orbit operation. For years, Joseph Allen and Daniel Wilkinson at NOAA’s Space Environment Center kept a master file of reported satellite anomalies from commercial and military sources. The collection included well over 9000 incidents reported up until the 1990’s. This voluntary flow of information dried-up rather suddenly in 1998 as one satellite owner after another stopped providing these reports.

The 23rd Cycle – Satellite Insurance
“Like any insurance policy the average home owner tries to get, you have to deal with a broker and negotiate a package of coverages. In low risk areas, you pay a low annual premium, but you can pay higher premiums if you are a poor driver, live on an earthquake fault, or own beach property subject to hurricane flooding.

In the satellite business, just about every aspect of manufacturing, launching and operating a satellite can be insured, at rates that depend on the level of riskiness. Typically for a given satellite, 10-15 large insurers (called underwriters) and 20-30 smaller ones may participate. There are about 13 international insurance underwriters that provide about 75% or so of the total annual capacity. Typically, the satellite insurance premiums are from 8-15% for risks associated with the launch itself. In-orbit policies tend to be about 1.2 to 1.5% per year for a planned 10-15 year life span once a satellite survives its shakeout period. If a satellite experiences environmental or technological problems in orbit during the initial shakeout period, the insurance premium paid by the satellite owner can jump to 3.5 – 3.7% for the duration of the satellite’s lifetime. This is the only avenue that insurers have currently agreed upon to protect themselves against the possibility of a complete satellite failure. Once an insurance policy is negotiated, the only way that an insurer can avoid paying out on the full cost of the satellite is in the event of war, a nuclear detonation, confiscation, electromagnetic interference or willful acts by the satellite owner that jeopardize the satellite.

There is no provision for ‘Acts of God’ such as solar storms or other environmental problems. Insurers assume that if a satellite is sensitive to space weather effects, this will show up in the reliability of the satellite, which would then cause the insurer to invoke the higher premium rates during the remaining life of the satellite. Insurers, currently, do not pay any attention to the solar cycle, but only assess risk based on the past history of the satellite’s technology.

As you can well imagine, the relationship between underwriters and the satellite industry is both complicated and at times volatile. Most of the time it can be characterized as cooperative because of the mutual interdependencies between underwriters and satellite owners. During bad years [like 1998 for example] underwriters can lose their hats and make hardly any profit from this calculated risk-taking. Over the long term, however, satellite insurance can be a stable source of revenue and profit, especially when the portion of their risk due to launch mishaps is factored out of the equation. As the Cox Report notes about all of this, “The satellite owner has every incentive to place the satellite in orbit and make it operational because obtaining an insurance settlement in the event of a loss does not help the owner continue to operate its telecommunications business in the future. To increase the client’s motivation to complete the project successfully, underwriters will also ask the client to retail a percentage [typically 20%] of the risk” [Cox Report, 1999]

According to Philippe-Alain Duflot, Director of the Commercial Division of AGF France,
“…the main space insurance players have built up long-term relations of trust with the main space industry players, which is to say the launch service providers, satellite manufacturers and operators. And these sustained relations are not going to be called into question on the account of a accident or series of unfortunate incidents”. Still, there are disputes that emerge which are now leading to significant changes in this relationship. Satellite owners, for instance, sometimes claim a complete loss on a satellite after it reaches orbit, even if a sizable fraction of its operating capacity remains intact after a ‘glitch’. According to Peter D. Nesgos of the New York law firm Winthrop, Stimson, Putnam and Roberts as quoted by Space News, “In more than a dozen recent cases, anomalies have occurred on satellites whose operators say they can no longer fulfill their business plans, even though part of the satellite’s capacity can still be used.”

This has caused insurance brokers to rethink how they write their policies, and for insurance underwriters to insist on provisions for partial salvage of the satellite. In 1995, the Koreasat-1 telecommunications satellite owned by Korea Telecom of South Korea triggered just such a dispute. In a more recent dispute underwriters actually sued a satellite manufacturer Spar Aerospace of Mississauga, Canada over the AMSC-1 satellite, demanding a full reimbursment of $135 million. They allege that the manufacturer ‘covered up test data that showed a Spar-built component was defective’. Some insurers are beginning to balk at vague language which seemingly gives satellite owners a blank check to force underwriters to insure just about anything the owners wish to insist on.

One obvious reason why satellite owners are openly adverse to admitting that space weather is a factor, is that it can jeopardize reliability estimates for their technology, and thus impact the negotiation between owner and underwriter. If the underwriter deems your satellite poorly designed to mitigate against radiation damage or other impulsive space weather events, they may elect to levy a higher premium rate during the in-orbit phase of the policy. They may also offer you a ‘launch plus five year’ rather than a ‘launch plus one year’ shakeout period. This issue is becoming a volatile one. A growing number of stories in the trade journals since 1997 report that insurance companies are growing increasingly vexed by what they see as a decline in manufacturing techniques and quality control. In a rush to make satellites lighter and more sophisticated, owners such as Iridium LLC are willing to loose six satellites per year. What usually isn’t mentioned is that they also request payment from their satellite insurance policy on these losses, and the underwriters then have to pay out tens of millions of dollars per satellite. In essence, the underwriter is forced to pay the owner for using risky satellite designs, even though this works against the whole idea of an underwriter charging higher rates for known risk factors. Of course, when the terms of the policy are negotiated, underwriters are fully aware of this planned risk and failure rate, but are willing to accept this risk in order to profit from the other less risky elements of the agreement. It is hard to turn-down a five year policy on a $4 billion network that will only cost them a few hundred million in eventual payouts. The fact is that insurers will insure just about anything that commercial satellite owners can put in orbit, so long as the owners are willing to pay the higher premiums. Space weather enters the equation because, at least publicly, it is a wild card that underwriters have not fully taken into consideration. They seemingly charge the same in-orbit rates (1.2 to 3.7%) regardless of which portion of the solar cycle we are in.

More and more often, satellite insurance companies are finding themselves in the position of paying-out claims, but not for the very familiar risk of launching the satellite with a particular rocket. In the past, the biggest liability was in launch vehicle failures, not in satellite technology. As more satellites have been placed in orbit successfully, a new body of insurance claims has also grown at an unexpected rate. According to Jeffrey Cassidy, senior vice president of the aerospace division of A.C.E. Insurance Company Ltd., as many as 11 satellites during 1996 have had insured losses during their first year of operation. The identities of these satellites, however, were not divulged nor even the names of their owners.

Despite the rough times that both manufacturers and insurers seem to be having, they are both grimly determined to continue their investments. Assicurazioni Generali, S.p.A of Triests, the biggest underwriter has no plans to reduce its participation in space coverage, but at the same time thinks very poorly of the satellite manufacturing process itself. Giovanni Gobbo, Assicurazioni’s space department manager, is quoted as saying “I would not buy a household appliance that had as many reliability problems as today’s satellites”. The biggest pay out in 1998 was for $254 million for 12 satellites in the Iridium program; five were destroyed at launch.

Despite all the dramatic failures, the satellite insurance companies have actually lowered their insurance rates for launches from 15-16% in 1996 to 12-13% in 1997. Meanwhile, in-orbit insurance rates, the kind affected by space weather problems, have remained at 1-2% per year of the total replacement cost. Industry insiders do not expect this pricing to remain so inexpensive. With more satellite failures expected in the next few years, these rates may increase dramatically.

The nearly $600 million in in-orbit satellite failures that insurance companies have had to pay on in 1998 alone, has prompted questions of whether spacecraft builders are cutting costs in some important way to increase profit margins especially with the number of satellite anomalies continuing to rise. Between 1995 and 1997, insurance companies paid out 38% of the $900 million in claims, just for on-orbit satellite difficulties. Since the early 1980’s, satellite failure claims have doubled in number, from $200 to $400 million annually. The satellite manufacturers argue that compared to the number of satellites launched and functioning normally, the percentage of anomalies and failures has remained nearly the same over the last two decades. Hughes Space and Communications, for example, has 67 satellites and there has been no percentage change in the failure rate. They use this to support the idea that the problems with satellite failures are inherent to the technology, not the satellite environment that changes with the solar cycle. According to Michael Houterman, president of Hughes Space and Communications International, Inc of Los Angeles, the spate of failures in the HS-601 satellites is a result of ‘design defects’ not of production-schedule pressure or poor workmanship: “Most of our quality problems can be traced back to component design defects. We need, and are working toward, more discipline in our design process so that we can ensure higher rates [of reliability]”.

Satellite analyst Timothy Logue at the Washington law firm of Coudert Brothers begs to differ: “The commercial satellite manufacturing industry went to a better, faster, cheaper approach, and it looks like reliability has suffered a bit, at least in the short term”. Curiously absent from virtually every communications satellite report of a problem, is the simple acknowledgment that space is not a benign environment for satellites. The bottom line in all of this is that communications technology has expanded its beachhead in near-earth space to include thousands of satellites. These complex systems seem to be remarkably robust, although for many of them that may be in the wrong place at the wrong time, their failure in orbit can be tied to solar storm events. The data, however, is sparse and circumstantial because we can never retrieve the satellites to determine what actually affected them. Satellite manufacturers often look for technological problems to explain why satellites fail, while scientists look at the spacecraft’s environment in space to find triggering events. What seems to be frustrating to the satellite manufacturing industry is that, when in-orbit malfunctions occur, each one seems to be unique. The manufacturers can find no obvious pattern to them. Like a tornado entering a trailer park, when space weather effects present themselves in complex ways across a trillion cubic miles of space, some satellites can be affected while others remain intact.

For years, Joseph Allen and Daniel Wilkinson at NOAA’s Space Environment Center kept a master file of reported satellite anomalies from commercial and military sources. The collection included well over 9000 incidents reported up until the 1990’s. This voluntary flow of information dried-up rather suddenly in 1998 as one satellite owner after another stopped providing these reports. From now on, access to information about satellite problems during Cycle 23 would be nearly impossible to obtain for scientific research. More than ever, examples of satellite problems would have to come from the occasional reports in the open trade literature, and these would only cover the most severe, and infrequent, full outages. There would be no easy record of the far more numerous daily and weekly mishaps, which had been the pattern implied by the frequency of these anomalies in the past.

2004 – Commercial Satellite Bus Reliability’ – Frost & Sullivan has analyzed the on-orbit performance of the major commercially available satellite buses and considered the strengths and weaknesses of their manufacturers in order to determine which satellite bus (or platform) is more reliable. Based on both Frost & Sullivan and Airclaims data, this study highlights reliability records, anomaly trends, and the impact of these factors on the insurance industry and hence, the satellite industry overall….In terms of satellite insurance claims, the period from 1998 through 2001 was particularly bad. The unusually high number of satellite anomalies and resulting insurance claims have seriously affected both the quality and reliability of services provided by commercial satellite operators and have (along with notable launch vehicle failures) had a negative impact on investors’ perceptions of the space industry as a whole. Beyond that, such problems have resulted in billions of dollars of losses for space insurance underwriters, increasing space insurance premium rates and hence the cost of ownership for commercial communications satellites in general. Although the last two years have seen a reduction in the number of serious anomalies the affects of the 1998-2001 period remain. Insurance costs have risen considerably and attitudes towards satellites and their manufacturers have changed. Before 1998 the satellite industry and its customers were moving toward a vision of satellites as a commodity. Satellites were expected to function well and new technologies to expand their capabilities were embraced. Satellite manufacturers built new manufacturing facilities and anticipated ever-increasing orders. This vision proved faulty when the new technologies showed flaws once in service and previously reliable satellites began to develop problems as well. The large market for satellites that had motivated the more production-orientated manufacturing techniques failed to appear and the commodity model of satellite manufacturing has now generally been abandoned. [Report from Frost & Sullivan]

2000 – Insurance industry funds new research into satellite failures” – The space insurance industry and the TSUNAMI initiative has put up £120,000 into two one-year research projects examining the role of space weather in satellite failures. Scientists from Mullard Space Science Laboratory and British Antarctic Survey (BAS) will attempt to match known violent space weather events with satellite failures using data from the space and from the ground. MSSL will also develop a spacecraft ‘black box’ to measure the amount of exposure to ‘killer’ electrons from the Sun. Space weather has been blamed for satellite failures that have cost the insurance industry billions of pounds. Solar conditions drive the space weather environment near Earth. Explosions on the Sun send gigawatts of energy hurtling towards Earth via the solar wind, causing space storms around Earth. This activity increases when the solar cycle reaches its peak every 11 years. This year sees the peak, making the studies even more urgent. Both projects will help space insurers minimize losses and set premiums. T he research funds are awarded by the Tsunami consortium, a group of scientists and insurers that was formed to stimulate new research proposals to improve understanding of natural hazards specifically to meet the needs of the industry. ” [BAS Press Release]

A consortium of Lloyd’s underwriters has formed a new facility for satellite insurance that will “enable the most accurate pricing of risks the sector has ever seen,” said an announcement on the Lloyd’s Website (www.lloyd’s.com). The consortium is adopting a new approach that will combine the market’s underwriting expertise with detailed intelligence on the reliability of satellites and their components. Liberty Syndicates formed the new venture in partnership with Sciemus, and will provide up to $400 million of insurance capacity for the sector. The facility is expected to create savings of more than $10 million a year for some satellite operators while enhancing insurers’ returns. The bulletin said the “consortium will provide a one-stop shop for coverage using data from a 40 year study carried out by the Ministry of Defense. The research will enable the consortium to individually tailor accurate prices according to the specific risk profile of each operator.”

The new approach is designed to eliminate the “fragmented” market for satellite coverage. Notably it “involves the broker agreeing to terms with a string of underwriters.” The announcement explained that the “lack of data surrounding the risks associated with satellite launches meant there was a blanket rate for coverage.” Jeffrey Wright, director of reinsurance at HSBC Insurance Brokers, one of the select few brokers with access to the capacity, observed that the approach was ground breaking. “It will revolutionize the approach and the underwriting of satellite risks. This is not about offering cheap insurance. It is about rewarding the best companies in the business with premiums, which reflect the risk. It brings accuracy and market leading technology and information to a sector which requires it.” The bulletin also explained: “Despite some high profile losses in the past, the Space industry has grown to an estimated capacity of $490 million for launch risks and $310 million for in-orbit risks for 2006. Insurance costs are often an operator’s second largest cost.”

Liberty Syndicates’ chief executive Sean Dalton commented: “This represents the largest single source of new capacity made to the industry, which hitherto has suffered from an inability to differentiate between good and bad operators. The model will enable differentiation between good and bad risks within the satellite sector, and price to reflect this. Operators will be able to see the benefit in terms of significant cost savings and certainty. “The model will also enable contract certainty and facilitate claims resolutions, an area that has caused all parties difficulties in the past due to imbalances in knowledge and desired outcomes,” he concluded.

Back reflection (return loss) is the ratio of the light backscattered or reflected in the reverse direction of the forward direction of travel. Back reflection limits and/or degrades system performance. Unlike attenuation, which can be reduced by cleaning the connector interfaces etc., the effects of back reflection can only be resolved by re-polishing connector faces, or even changing the type of connector interfaces such as UPC or APC connector polishes.